Proliferative vascular disorders can result in malformed vasculature, causing not only aesthetic concerns but, dependent upon location, a serious threat to a patient's health. For example, infantile hemangioma (IH) is a common childhood tumor composed of disorganized blood vessels and immature cells. IH results from a disruption of neonatal vasculogenesis, de novo formation of vessels from progenitor cells, angiogenesis, and a sprouting of new vessels from pre-existing vasculature. Although benign and usually a harmless tumor, some IH deform or destroy facial features and/or obstruct vision and breathing. Forty to eighty percent result in permanent cutaneous residua, which can be disfiguring. Corticosteroids are the traditional first-line therapy, however the adverse effects are numerous (Boon et al., Plast Reconstr Surg 1999 104:1616-1623) and approximately 16% of hemangiomas do not respond (Bennett et al., Arch Dermatol 2001 137:1208-1213). Propranolol has recently been introduced as a treatment for IH (Leaute-Labreze et al., N Engl J Med 2008 358:2649-2651) (Siegfried et al., N Engl J Med 2008 359:2846). However, its use is not without risks, and not all tumors respond (Frieden and Drolet. Pediatr Dermatol 2009 26:642-644). More effective therapies could improve outcomes and/or shorten treatment duration, thereby reducing the risk of adverse side effects.